The invention relates to a fuel injection pump for internal combustion engines as generically defined hereinafter. In a fuel injection pump of this kind, known from German Offenlegungsschrift 37 22 265, in order to divide the fuel injection quantity into a preinjection quantity and a main injection quantity, the high-pressure supply stroke is controlled by the first electrically controlled valve. This is accomplished by means of the closure of the line leading from the pump work chamber to a fuel supply chamber that is at low pressure; to thereby interrupt the high-pressure supply to the respective fuel injection nozzle, the initially closed second electrically controlled valve is then opened between the preinjection and the main injection, to thus enable a withdrawal of fuel into the reservoir chamber that lowers the supply pressure to below the injection valve opening pressure. Thus, upon the opening of the second electrically controlled valve, the preinjection is interrupted, and the main injection is begun once the withdrawal has ended. To this end, the second electrically controlled valve controls the relief of the rear side of the adjustable wall, which is thus blocked in terms of its deflection motion when the valve is closed.
This version has the disadvantage that the control of the preinjection quantity and of the main injection quantity is influenced by the control of the quantity transferred to the reservoir; in particular, the reservoir volume must determine not only the angular interval between the preinjection quantity and the main injection quantity but the magnitude of the preinjection quantity as well. The fact that the duration of fuel withdrawal in the high-pressure supply phase of the pump piston is rpm-dependent also must be taken into account. A further disadvantage is that the main injection is effected at a relatively high injection rate, because the middle, steeply ascending region of the cam is involved in the drive, which is operative in this range, of the pump piston by the drive cam.